For the past two years, the EU so-called troika of Britain, France and Germany has struggled to defuse the brewing crisis over Iran's nuclear ambitions.

The 30-page document just handed over to Tehran is the latest stab at a compromise.

On the face of it, it is a classic mix of carrot and stick.

Some
inducements build on work-in-progress: speeding up negotiations on an EU Iranian trade agreement, more support for Iran's application to join the Word Trade Organization.

It also offers enhanced consultation on drug smuggling, terrorism and relations with Iran's two turbulent neighbours, Iraq and Afghanistan.

Some provide rhetorical reassurance: confirmation that Iran has the right to develop a civilian nuclear programme, and recognition that Iran's territory and political independence should not be threatened.

And some are designed to counter specific objections: the offer to allow Western companies to tender for nuclear contracts in Iran, and the idea that some third country might hold five years' supply of nuclear fuel in reserve.

These are aimed at answering Iran's complaint that reliance on a single outside supplier could jeopardise its national security.

Stalemate

But when it comes to the main disagreement between the two sides, the EU position has not budged an inch from earlier negotiations.

The bottom line is, and was, that Iran must agree not to convert or enrich its own nuclear fuel - activities which the EU and US fear could give it access to weapons-grade uranium or plutonium - but instead import all the nuclear fuel it needs, and export all spent fuel.

Work could re-start at Isfahan next week

Only then, argues the EU troika, can concerns that Iran is seeking to develop a secret nuclear weapons programme be laid to rest.

So what happens now?

The Iranians have said they will mull over the offer and respond in a few days.

All along, they have insisted their nuclear programme is peaceful and they are within their international rights to develop the full fuel cycle.

And they have said they have run out of patience and intend to resume the conversion of fuel at their Isfahan nuclear plant next week.

They have even asked officials from the UN's nuclear agency to be present to monitor what they do.

So in the absence of any fundamental new concessions from the EU, it seems unlikely their position will soften.

Ground work

In European capitals, diplomats are still hoping that the Iranians might be playing a game of brinkmanship and may stop short of restarting the conversion process.

"It's not what Iran says that is important, it's what it does," said one British diplomat.

It's not definitive. It's a framework for negotiations

Unnamed European diplomat

So the EU three are bringing all diplomatic pressure they can to bear.

They have let it be known they are prepared to carry on talking to Tehran, even if they rebuff this latest offer.

"It's not definitive. It's a framework for negotiations," said one source.

And they have called an emergency meeting of the International Atomic Energy Agency (IAEA) on Tuesday to urge Iran not to take any action.

But the crunch will come if - once IAEA officials and their monitoring equipment arrive in the middle of next week - the Iranians go ahead with their threat and restart the Isfahan conversion process.

That, say EU diplomats, could well bring the negotiating process of the past two years to an abrupt end.

Double-standards?

The next step would be to ask the IAEA board at its next meeting in September to refer the whole question to the UN Security Council, which in theory could impose sanctions.

But that is not a straightforward path. Persuading IAEA board members and the Security Council to take such a drastic step might not be easy.

Although there is plenty of unease, there is no clear proof of Iran's military intentions or of the danger they might represent.

A recent US intelligence assessment backed away from a previous estimate of five years and now guesses it might take 10 years for Iran to acquire nuclear weapons.

And then there is the question of consistency.

Iran repeatedly asks why the US is prepared to improve relations with other countries, such as India and Pakistan, that have acquired nuclear weapons in flagrant disregard for international safeguards, while Iran, which it claims has abided by its obligations, is treated like a pariah.

This is a brewing crisis that has taken over two years to come to a head, but do not expect any dramatic resolution soon.